1. Technical Field
The present invention relates to a method and apparatus for data processing in general, and in particular to a method and apparatus for processing audio data within a data-processing system. Still more particularly, the present invention relates to a method and apparatus for providing audio sample rate conversion within a data-processing system.
2. Description of the Prior Art
Audio presentation is one of many integral features of a personal computer (PC) system equipped with multimedia capabilities. Typically, audio presentation support is provided by means of either adding an audio add-on board (commonly known as a sound card) to a system board of the PC system or integrating similar hardware within the system board. In both cases, integrated audio codecs are usually utilized to support the audio function. The problem with integrated audio codecs is that a relatively sensitive analog circuit is placed in close proximity to a relatively noisy digital audio circuit. As a result, the quality of audio presentation is not even comparable with that of an average home stereo.
In an effort to correct the above-mentioned problem, a specification known as the Audio Codec ""97 (AC 97) was introduced, with the support of Intel Corporation and virtually all other audio integrated-circuit device manufacturers such as Analog Devices, National Semiconductor, etc. According to the AC 97 specification, analog and digital audio functions in a PC system environment must be performed by two separate components, namely, an analog audio codec and a digital audio controller. Moreover, interface and pinout of analog codecs are standardized in a way that an original equipment manufacturer (OEM) can mix and match analog codecs and digital controllers from different vendors. Additionally, the analog codec is defined to operate only at a sample rate of 48 kHz, utilizing up to 20-bit samples.
Despite of all the advantages provided by the AC 97 specification, the rigidity of 48 kHz sample rate presents some problems when interfacing legacy devices having a sample rate other than 48 kHz with an AC 97 compliant system. As an attempt to provide a solution to such problems, the abovementioned copending application describes a method and apparatus for providing audio sample rate conversion within a data-processing system having a digital audio controller that conforms to the AC 97 specification. It is an objective of the present disclosure to describe an improved method and apparatus to solve the same problem.
In view of the foregoing, it is therefore an object of the present invention to provide an improved method and apparatus for data processing.
It is another object of the present invention to provide an improved method and apparatus for processing audio data within a data-processing system.
It is yet another object of the present invention to provide an improved method and apparatus for providing audio sample rate conversion within a data-processing system.
In accordance with a method and apparatus of the present invention, an audio data stream having an input sample rate is first received. A sampling frequency ratio of the input sample rate to a selected output sample rate is determined, and this sampling frequency ratio is then utilized to compute output samples. The output samples are subsequently filtered with a lowpass filter and output at the selected output sample rate.
All objects, features, and advantages of the present invention will become apparent in the following detailed written description.